EFFECTS OF A HUMAN-MADE ENVRIONMENTAL BARRIER TO GENE FLOW IN A SEMI-AQUATIC 
TURTLE, Trachemys scripta ON THE MISSISSIPPI RIVER

Lyndon M. Coghill1, Michael A. Romano1, Brian Sloss2, and Ryan Franckowiak2
1Western Illinois Univeristy, 1 University Circle, Department of Biological 
Sciences Waggoner Hall, Macomb IL, 61455.  2College of Natural Resources, Univ. 
of Wisconsin-Stevens Point
800 Reserve Street, Stevens Point, WI  USA  54481.
      
      In the past 50 years the state of Illinois has lost almost 90% of its 
original vegetation and drained over 90% of its original wetlands. Almost all of 
Illinois rivers have been channeled and dammed to control the water for shipping 
and agricultural use. Extensive pollution has caused many problems, and has an 
increased effect on aquatic and semi-aquatic organisms. 
      The channeling of the Mississippi River in non-natural courses often 
creates an unnatural, impassable barrier to aquatic and semi-aquatic organisms. 
This loss of biodiversity should be cause for alarm. Aquatic and semi-aquatic 
organisms are often precursors of larger problems with loss of biodiversity and 
pollution. One way to determine if a population has significant levels of gene 
flow in order to maintain healthy metapopulations is to use microsatellite DNA 
to examine the levels of gene flow among varying populations. Microsatellites 
have both the resolution and power to adequately examine the levels of gene flow 
in given populations. In this study we are examining whether the only true 
spillway dam system left on the Mississippi River, as well as the oldest dam on 
the river system, is a barrier to semi-aquatic organisms such as turtles. 
      In this study, tissue samples were taken from the freshwater river turtle 
Trachemys scripta trapped at 4 different locations along the Mississippi River.  
Trachemys scripta was chosen because it has one of the largest habitat ranges of 
any North American freshwater turtle. The first site is located directly above 
Lock and Dam 19. One site below the dam on the Illinois side of the river is 
located at Eagle Island Slough. The other two sites are on the Iowa side of the 
river; this was chosen because the lock which allows water flow back and forth 
across the dam is located on the Iowa side of the river. The first site is the 
Des Moines River which separates the state of Missouri and Iowa. The second site 
is further downstream in an island slough, in the proximity of the mouth of the 
Fox River system. The samples were stored in 95% ethanol. The samples then had 
their DNA extracted, and 5 individual microsatellite loci were amplified using 
PCR.
      Preliminary data using allozyme studies have shown that there is some 
level of gene flow across the dam to the downstream side. With the increased 
resolution of microsatellites the preliminary data is showing that there is a 
high amount of variation in the Fox River system. This suggests that 1-way gene 
flow is occurring from above the dam to below the dam, down the Iowa side of the 
river. This is consistent with the hypothesis that the turtles are getting into 
the lock system above the dam, and the current from the spillway system is 
sweeping them downstream on the Iowa side.  The turtles, however, are not 
crossing the river to the Illinois side and there is no lock on the Illinois 
side to allow the turtles to move downstream on that side of the river. There is 
also no evidence of gene flow moving from below the dam to above the dam through 
the lock system.
      
Keywords: turtle, Mississippi River, Trachemys scripta, microsatellite DNA, gene 
flow